Patent GB-789848-A (GB)
Title: Automatic weighing scale
IPC: G01G23/00
Filed: 1956-02-15
Abstract: 789,848. Weighing apparatus. THAYER, F. L., and THAYER, W. L. Feb. 15, 1956, No. 4694/56. Class 143 [Also in Groups XXXVIII and XL(b)] A weighing scale comprises a base, a lever system, a scale platform supported on the lever system, a damped weigh beam connected to the lever system and vertically disposed spring metal flexure plates for suspending the platform and lever system from the base, the fulcra of the beam and lever system being arranged in conjunction with the disposition of masses in the lever system to give rise to particular forces whereby to bring the beam to a balance position when a given weight is on the platform, said flexure plates resisting deflection of the beam away from the balance position by a force substantially greater than the pendular forces. An endless belt weighing platform 94 (Fig. 2). driven by a reversible electric motor 98 is supported through legs 34, 35 and pairs of spring plates 36. 37 from torsion bars 26, 27 which are suspended from fixed frame members 22, 23 by pairs of spring plates 28, 29, and which carry levers 38, 39 interconnected by a spring plate 40. Depending from a spring plate 41 on arm 39 is a U-shaped draft rod 42 which is connected through a pair of spring plates 46 (see also Fig. 9) on the weigh beam 44 which is fulcrummed on a spring plate 50 secured to a fixed frame memiber 52. A dash pot 68 is set to critically clamp the beam. The beam carries a non-rotatahle poise weight (not shown) which is traversed along the beam by a motor 70 driving a screw 60 through gears 72, 74, the pitch circles of which intersect on the axis of the beam fulcrum. The free end of the beam carries a plate 66 which intercepts. a beam of light, falling on a photo cell 90, and mercury contacts 92. The motor 70 also drives a weight indicator 87, a printing device (not shown) which records the indicated weight and the totalized weight when actuated by 'the relay circuit shown in Fig. 15, and a cam shaft (also not shown) the cams on which operate switches 79, 81, 83, 85 (Fig. 15) in accordance with the position of the poise. When used for check weighing and rejecting under or over weight articles the cycle of operations is as follows. With the belt 94 empty the beam drops so making mercury contacts 92 which energize relays 161, 162 which cause the motor 70 to traverse the poise inwardly until cam switch 79 is opened. When the platform is loaded the beam rises and intercepts the beam of light falling on cell 90 which then, by means of relay 168, energizes relay 163 which causes motor 70 to traverse the poise outwards 'until the beam drops below cell 90, or until cam operated switch 85 is opened, either of which de-energizes relay 163. 'This causes the weight recorder 86 to be operated and relay 164 to be energized. Relay 164 then energizes relays 161, 162, so driving the poise inwardly, and, simultaneously energizes relay 165 which functions to energize the belt driving motor 98 in a "correct weight" discharge direction. Relays 164, 165 are de-energized when switch 79 is operated. Should an article be of incorrect weight, a relay 166 is energized by switch 81 or 83 being closed when relay. 163 is de-energized, and this causes a reversal of motor 98 which then rejects the article by moving the belt in the reverse direction. The circuit is pro. vided with a switch 154 which isolates switches 79, 81, 83, 85 and allows the apparatus to be used for weighing articles of any weight within the range of the scale. For test purposes a switch 156 is provided to isolate the discharge motor 98. In a modification, Fig. 11, the endless belt is replaced by a platform 104 which is tiltable in any of three directions, corresponding with correct, under or over weight, by a pneumatic thrustor 114, the direction being determined according to which of three solenoid operated latches 121 are engaged with bars 106 on the platform. These latches are selectively energized by a relay circuit (Fig. 16, not shown) under the control of the previously described weighing mechanism.